The Carmacks Copper Project is designed as an open-pit mine with acid heap leaching and solvent extraction/electrowinning (SX/EW) to produce LME Grade A copper cathode.
Report context
This technical report is dated 31 October 2012 and describes the proposed Carmacks Copper Project. The project is planned as an open-pit mine with an acid heap leach and SX/EW processing facility. The report presents the design basis for the process plant, associated infrastructure, and utilities.
Processing route
Mining and crushing
The mining operation is designed to produce an average 1.775 million tonnes of ore per year, or approximately 28,400 tonnes (ore and waste) per day on a seven-day-per-week, 24-hour-per-day operation. The mine will be operated year round but may temporarily suspend ore stacking operations when winter temperatures are extreme.
Mining equipment is planned to comprise 10.5 cubic metre hydraulic excavators, 11.5 m³ loaders, and 91-tonne haul trucks. Ore will be hauled by truck and dumped directly into the primary crusher, from where it will be conveyed to secondary and tertiary crushers. The final product will have a maximum size of 19 mm and a P80 of 13 mm.
Agglomeration and heap leaching
The crushed product will first be agglomerated with sulphuric acid and water, then conveyed by a series of overland (grasshopper) conveyors to a lined valley fill leach pad where it will be placed by means of a radial stacker. An Events Pond is located down gradient from the leach pad to provide capacity for an emergency drain down of the pad and to manage the plant water balance during various storm events.
The crushed ore on the leach pad will be irrigated with dilute sulphuric acid to leach copper from the ore. Pregnant leach solution (PLS) will be collected and pumped to the solvent extraction plant.
Solvent extraction
The SX plant will consist of three mixer-settlers: two for extraction of the copper from the PLS (aqueous phase) into an organic phase containing an extractant reagent, and one for stripping the copper from the organic phase into a strong acid solution (the electrolyte). The two extraction mixer settlers will operate in series with the aqueous and organic flowing counter to one another. In extraction, the transfer of copper from the PLS to the organic will be accompanied by the transfer of an equivalent amount of acid from the organic to the aqueous. The aqueous phase after extraction of most of the copper is called the raffinate. The raffinate will be pumped back to the heap to leach more copper.
In the single strip unit, the loaded organic will be contacted with a strong acid solution, causing the extraction reaction to reverse and transferring the copper from the organic to the electrolyte while an equivalent amount of acid transfers from the electrolyte to the organic. The acid contained in the electrolyte is generated in the electrowinning cells. From the stripper settler, the organic will return to the second of the two extraction mixer settlers, while the electrolyte (the rich electrolyte) enriched in copper advances to the electrowinning cells in the tankhouse.
Electrowinning and product handling
A direct electric current is passed through the cells, causing the copper to plate out onto permanent stainless steel cathode blanks and generating acid at the anode. From the tankhouse, the (lean) electrolyte returns to the strip mixer settler. The copper will be harvested on a weekly basis. Copper produced by this process, LME grade A, will be weighed and bundled into 2 to 3 tonne packages for sale on the world market.
Sulphuric acid plant
Sulphuric acid is produced on site by means of a 131 tonne per day sulphuric acid plant. The plant will burn sulphur which will be transported to site in liquid form. Storage tanks will be provided for liquid sulphur to accommodate potential supply interruptions and for the concentrated acid to accommodate variations in demand for acid and allow for plant maintenance shutdowns.
Reagent handling
Storage, mixing, and distribution are provided for other process reagents such as diluent, extractant, guartec, and cobalt sulphate.
Utilities
The report states that CNMC anticipates Yukon Energy Corp. (YEC) will serve the mine from an existing Carmacks-Stewart 138 kV transmission line along the existing Klondike Highway. A new substation (tap-off) in the vicinity of McGregor Creek would feed an 11-kilometre 34.5 kV transmission spur line to the mine's main substation terminating on a dead-end structure. The schedule for completion of this spur line is the third quarter of 2015. CNMC has a secure right-of-way for the power line from McGregor Creek to the site and is in discussions with YEC over terms of a future power supply agreement. Total project electrical load is estimated to be about 10 megavolt-amperes (MVA). The mine is not a significant electrical power consumer, as all major mining equipment is proposed to be diesel powered.
Total fresh make-up water required varies depending on precipitation but is expected to peak at a monthly average of about 27 m³/hr. Approximately 45 m³/day of potable water will be required and the remainder will go to the process. Potable water will be produced by means of a packaged treatment plant. Mine road watering will average about 190 tonnes per day, but that quantity is assumed to come from collected runoff and mine water infiltration. Fresh water supply wells will be located in the bedrock-confined aquifer underlying the Williams Creek drainage. Each well will have the capacity to produce about 150 m³/day of fresh water. The fire water requirement is 280 m³/hr for two hours, to be satisfied by providing a dedicated fire reserve capacity of 560 m³ in the lower portion of the fresh and firewater tank.
Ancillary facilities
Other facilities at site will include: a Truck Shop providing adequate space for the maintenance of two 91-tonne trucks and associated warehousing; an Administration building; a Laboratory facility; an Operations Camp to accommodate non-local workers; and a Gatehouse/First Aid post.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Annual copper production (average) | 13,200 tonnes LME Grade A cathode | Proposed design |
| Annual ore feed rate (average) | 1.775 million tonnes | Proposed design |
| Daily ore and waste production | 28,400 tonnes per day | Proposed design |
| Crushed product maximum size | 19 mm | Proposed design |
| Crushed product P80 | 13 mm | Proposed design |
| Mining equipment – excavator | 10.5 m³ | Proposed design |
| Mining equipment – loader | 11.5 m³ | Proposed design |
| Mining equipment – haul truck | 91-tonne | Proposed design |
| Sulphuric acid plant capacity | 131 tonnes per day | Proposed design |
| SX plant configuration | Three mixer-settlers (two extraction, one strip) | Proposed design |
| Total project electrical load | 10 MVA | Proposed design |
| Fresh make-up water (peak monthly average) | 27 m³/hr | Proposed design |
| Potable water requirement | 45 m³/day | Proposed design |
| Fire water requirement | 280 m³/hr for 2 hours | Proposed design |
| Fire reserve capacity | 560 m³ | Proposed design |
| Fresh water well capacity (each) | 150 m³/day | Proposed design |
| Mine road watering (average) | 190 tonnes per day | Proposed design |
| Cathode harvesting frequency | Weekly | Proposed design |
| Cathode bundle size | 2 to 3 tonnes | Proposed design |
Project website: https://cascadiaminerals.com/cascadia-completes-drill-program-at-its-carmacks-copper-gold-project-yukon/
Technical qualifications
This technical report presents a proposed design for the Carmacks Copper Project. No historical operating data or testwork results are provided in the processing sections of the report. The report does not include actual performance data, operating results, or confirmed metallurgical recoveries. All values presented are design targets for the proposed operation. The process description is based on the proposed flowsheet as shown in Figure 1-4 (referenced but not reproduced in the extracted text).
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Source: Carmacks Copper Project , Form 43-101F1 Technical Report, 31 October 2012, Section 17 Recovery Methods.
